Motorized doors comprising a shutter are commonly used to shut off openings, particularly in warehouses or industrial halls. These shutters are often made up of large flexible tarpaulins the lateral edges of which comprising beads which slide in guiding rails situated on each side of the opening that is to be closed. Alternatively, they can be made of rigid panels hinged to one another side by side or the shutter can be a rigid panel. Automatic doors are particularly useful when they are used to separate two rooms having different environmental conditions, such as temperature, relative humidity and the like, and more particularly to separate an indoor space from outdoor. Doors able to open and close at high speed are also known for these applications and are often referred to as “fast doors”.
One issue with motorized doors, particularly with fast doors due to their high closing speed, is impacts with obstacles accidentally located within the closing trajectory of the shutter. Besides damaging the obstacle (which can be a human) such impact can damage the leading edge of the shutter and also disengage the bead of the shutter lateral edges from the guiding rail. Systems for automatically reinserting a bead thus disengaged are described e.g., in US20100181033, which disclosure is herein incorporated in its entirety by reference.
Since preventing is better than repairing, many motorized doors have been developed comprising (a) detection cells suitable for detecting an accidental event and (b) a control system programmed for implementing a safety function aimed at managing the accidental presence of obstacles, in particular by stopping the door in its travel when it encounters one and moving it away from the obstacle in order to allow the removal thereof.
Various types of detection cells for detecting an accidental event are known in the art. Contactless detection systems, i.e., enabling an obstacle to be detected before impact, are disclosed e.g., in U.S. Pat. No. 7,034,686 with a proximity detector provided with an antenna, which triggers a command to stop and reverses the closure of the vertical door when the magnetic field created by the antenna is disturbed by an foreign object. This system has the advantage of preventing an impact, but it has the drawback of lacking precision given that the magnetic field may radiate outside the closure plane and thus cause false alarms triggered by objects situated close to the door but not underneath it. Optical sensors are also available which are able to detect the presence of a foreign body within the trajectory of the shutter.
An accidental event detection cell can comprise contact detectors as disclosed for example in US2007/0261305. Alternatively, some detection cells are based on the comparison with a reference value of parameters such as the motor torque, motor energy consumption, or shutter closing speed, such as in U.S. Pat. No. 5,198,974. A person skilled in the art therefore has a selection of detection cells to choose from for detecting an accidental event. The safety of a door requires, however, that a safety function be triggered upon detection of an accidental event. In particular, such safety function always includes stopping the closing motion of the shutter and often comprises reversing the direction of the motion to open the shutter, with variations as up to which re-opening position the shutter should be re-opened, whether or not the shutter should be closed again after reaching its re-opening position, the re-opening and/or re-closing speeds of the shutter, and the like.
U.S. Pat. Nos. 7,034,682, 6,989,767, 5,198,974 and US2007/0261305 concern safety systems for doors in which, as soon as an accidental event is detected, the motor stops, reverses its direction of rotation in order to open the door completely and stops definitively when the door is completely open. The door can be closed once again by manual intervention.
U.S. Pat. No. 4,452,292 concerns a door control system wherein an unwanted opening or closing of a shutter which has been previously locked is identified by a detection cell measuring an increase of the motor energy consumption. As illustrated in FIG. 2(b), mixed line, a control system stops the movement of the shutter for a period of time, after which the initial movement is resumed. In case a higher energy consumption is detected again, the shutter is stopped again for a given period of time. This control system is not suitable for protecting neither the shutter nor an obstacle, since absent a reversal of the movement in the opening direction, it is difficult or, in some cases, even impossible to remove such obstacle.
US20120073200 discloses a control system triggering a safety function upon detection of an accidental event comprising, as illustrated in FIG. 2(b), dashed line; the steps of (a) stopping the motion of the shutter and storing the position of impact, (b) reversing the movement and opening the shutter up to a waiting position, (c) after a predetermined period of time, reversing the movement again to close the shutter at a first speed, V1, until the shutter reaches a position located at a predetermined distance upstream from the stored position of impact, at which point (d) the closing speed is reduced to V3<V1, until the shutter passes by and proceeds beyond the position of impact at which point absent a new impact at said position, (e) the closing velocity is increased back to V1.
None of the known detection cells and control systems is able to identify the nature of an accidental event. For example, strong winds may apply a force onto the shutter of the door which increases the friction forces between the edges of the shutter and guiding rails to a point where the detection cells send a signal to the control system, which may be wrongly interpreted as an accidental event requiring the triggering of a safety function. The shutter is then stopped, its motion reversed to re-open the shutter, and reversed again to close it again. If the wind keeps blowing, the same signal can be sent again by the detection cells and, again, be wrongly interpreted by the control system which would trigger the safety function again, thus initiating a sequence referred to in the art as a “yo-yo” effect, which is of course undesirable. Keeping the shutter in its open position is, of course, not an acceptable solution, since the shutter is there to protect the interior of a room from inter alia external winds.
There therefore remains a need in the art for a safety door provided with detection cells and control system, which is potentially exposed to winds and can nonetheless be closed even in case of strong winds blowing. The present invention provides a wind-safe motorized door capable of automatically closing a shutter even when exposed to strong winds and thus avoiding the yo-yo effect. This and other advantages of the present invention are presented in continuation.